Pressurised light twin question

arj1 wrote:

Well, if it is a six-seater, then losing two theoretical passengers should be acceptable for some?
Although, I have to agree that for others it is not.

The 1999kg STC will do that to all of them. If I am not mistaken, the Seneca II’s max weight is almost identical to the 337, so also it becomes a 2-3 seater in Europe.

arj1 wrote:

Diamonds DAx2? And Tecnam P2006T.

The DA42 is certainly a very valid airframe yes. Out of my radar due to price mostly.
The Tecnam, not so sure about it. It reminds me a bit of the old Apache, in the sense that it has no performance to speak of, particularly OEI.

Which does indeed remind me that there are some I forgot: The Piper Apache was Pipers first twin at all. And there is the Piper Seminole (basically a twin engined Arrow) and the Beech Duchess.

The first seneca is a good bargain just for that, in addition to non-turbo engine. Friends in the club are still looking for such plane in good shape, such good planes are not staying long on the market.

Isn’t there a variation on the Piper Apache called the Geronimo which is supposed to have much better performance than the original, but again it is not pressurised.

There were also Polish twins which look very much like Senecas. I have forgotten what they are named now, but occasionally they come up on Plane Check.

L200 Morava

1950kg MTOW

I flew in one, in the 1960s.

Whoops

I quite like the look of that, I don’t know why.

greg_mp wrote:

The first seneca is a good bargain just for that, in addition to non-turbo engine. Friends in the club are still looking for such plane in good shape, such good planes are not staying long on the market.

There was a great Seneca I for sale in Italy a while ago, with Aspen and all for around 50k Euros. It was gone in several days. Currently there is one more in Italy, but I don’t know how good it is. There was one in Switzerland which got sold to Croatia I believe but was crash landed shortly after.

I flew the Seneca I for a while (HB-LEX) and it was a great short range airplane. The one I flew had Rajay Turbos (like the Turbo-Twin Commanche) and the full Piper Altimatic 3 AP, it was a delightful plane to fly. It was sold for a pittance and if I had known at the time, I would have snapped it up.

In some ways the Seneca I is underestimated. It has some lacking, but looking at the POH, it actually is not as bad as even I thought before. The POH does not help really a lot because it is really marginal and is still of the “edited by the marketing department” feel: mph instead of kt (looks better), no Time/Fuel/Distance tables, e.t.c.

Weak point is single engine service ceiling and climb. In fact, the Seneca I can hold somewhere between 4000 and 6000 ft AMSL with one engine out, provided the failure occurrs right there or actually above. It can drift down from 15000 ft at about 250 fpm, which still gives quite a long way to go until you need to find flat lands. But it is no cross the alps in IMC twin safety airplane.

Well, I had a look at it once again at the performance and made some quick and dirty calcs (to stay in practice….). And alas after some Excel Acrobatics, the Seneca I does not come out that badly as a traveller. Fuel flow is quite low if you think about it: 20.6 for 75% and about 14 GPH at 45%… So realistically between 16 and 18 GPH for both engines. Quite a few SEP’s do that with one engine alone.

After converting mph/kt, creating a TFD to climb table and calculating the resulting range including climb and a 45 min reserve, the results are as follows: (Disclaimer, don’t use any of this for actual planning…)

So the Seneca I can do:
Max speed of about 160 kts at 75% at 6000 ft.
Max speed at 65% is 159kt @ 9000 ft.
Max speed at 55% is 152kt @ 13000 ft
Max speed at 45% is realistically around 140 kt between 15000 and where ever it can reach.

Fairly typical for a non turbo airplane I’d think.

This I expected. 3.5 hours balls to the wall and up to 5.5. hrs in yawn mode

This however is a surprise.
Balls to the wall, the Seneca I can do 600 NM 6000 ft. I somehow am hesitant to believe the 162 kts however.
Best range would be about 750 NM at 45% and somewhere about 12-14k ft but it takes around 5 hrs to get there.
At breathable altitudes of around 10000 ft a range of about 650 to 700 NM at around 150 kt is a good indicator.

Realistically, IFR, this plane is a good 550 NM airplane, given that you need alternate and final reserves.

Looks like I need to run these calcs also on the Seneca II at some stage.